Cylinder or cylinder liner and method for producing the same



United States Patent [72] Inventor Yoshio Mori Tokyo, Japan [21] Appl. No. 705,693 [221 Filed Feb. 15, 1968 [45] Patented Sept. 29, I970 [73] Assignee Nippon Piston Ring Co., Ltd. Tokyo, Japan [32] Priority Feb. 15, 1967 [3 3 1 Japan [31 1 42/9,709

[54] CYLINDER 0R CYLINDER LINER AND METHOD FOR PRODUCING THE SAME 2 Claims, 3 Drawing Figs.

[52] U.S.Cl 92/168, 92/170, 308/23 8 [51] Int. Cl F16j 15/18, F01b 11/02, F16c 33/30 [50] Field of Search 92/ I 68, I70; 308/23 8 [56] References Cited UNITED STATES PATENTS 1,825,678 10/1931 Pittman 308/238X 2,689,380 9/1954 Tait 308/238X Primary Examiner-Martin P. Schwadron Assistant Examiner-Leslie J. Payne Attorney-Sughrue, RothweIl, Mion, Zinn and Macpeak ABSTRACT: A method for finishing a surface of a cylinder liner comprising, working the surface formed of a wear resistant metal so that it has a roughness within the range in which it is easily workable, and depositing a synthetic resin layer on the surface, said layer having a thickness at least greater than the roughness of the surface to compensate for the lack of running'in-properties due to the lack of smoothness due to working.

Patented Sept. 29, 1970 3,530,772

THICKNESS 0F RESIN LAYER FIGI ROUGHNESS OF SURFACE (40 FIG?) INVENT OR YOSHIO MORI BY 5%, M WAC/M ATTORNEYS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a cylinder or cylinder liner (hereinafter it is called cylinder") having a high sliding property with the piston rings and to a method for working the inner surface of the cylinder or cylinder liner with high efficiency.

2. Description of the Prior Art A hard chromium plating of a wear-resistant metal coating on a sliding surface of a cylinder liner has been applied to prevent wear of the surface. When uncoated, the cylinder has been made of a wear-resistant alloy.

Known alloys or wear-resistant metal coatings are very hard, are difficult to work, and take much labor to maintain the required accuracy and roughness for an internal combustion engine.

In the case of roughness, for example, the most suitable roughness required for an internal combustion engine is from 0.4;. to 3 and if the roughness is larger than said value, the wear on a mating material (piston ring) increases.

On the contrary, wear-resistant material brings a reduction of work efficiency, namely, there is not so much reduction in work efficiency up to a certain degree, but the efficiency falls off rapidly after that degree is passed.

An object of the invention is to provide a method for producing a cylinder with good machineability and without increasing blow-by deterioration of running-in and lowering of wear-resistance.

SUMMARY OF THE INVENTION This invention is directed to a cylinder construction comprising a cylinder in which the sliding surface of the cylinder is formed of an alloy or a wear-resistant coating which is worked to a roughness within an easily workable range and is provided with a synthetic resin coating having good running-in-properties and having a thickness at least thicker than the roughness to prevent the lack of adaptability due to the lack of working.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows the relation between the roughness of the finished metal surface, and the thickness of the synthetic resin layer.

FIG. 2 represents a cylinder utilizing a particular embodiment of the present invention.

FIG. 3 represents a cylinder utilizing another particular embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION The melting point of synthetic resin used for coating differs in accordance with the kind of resin used, and if a resin is used, the melting point of which is higher than 200C. no melting of coating will occur during the operation of the cylinder.

Thermoplastic or thermosetting synthetic resins, for example, polytetrafluoroethylene, polyamide resins, such as nylon, or silicone resins, can be used as the coating material. Some suitable filling materials and additives can be mixed in the resin.

The material is coated on the sliding surface of physically and chemically treated wear-resistant, metal coating or alloy by means of a flowing, spraying or sintering method.

A wear-resistant metal coating means a coating such as a hard chromium plating or molybdenum coating, etc. Wear-resistant alloys include cast iron alloys and aluminum alloys and any other conventional wear-resistant alloys.

The thickness of the synthetic resin layer may be varied in accordance with the surface roughness and it is preferable to select the thickness within the range shown in FIG. 1.

FIG. 1 is the chart which shows the relation between the roughness of the finished surface and the thickness of synthetic resin layer. When the former is shown by x-axis and the latter by y-axis, the area a is shown by the expression It is not preferable to use the resin layer in the relationship shown in area 9. because the resin layer will readily be torn and will produce biased abrasion.

In the area 0, namely shown by the expression mg yg 1.6x+1,

is best and the value of a: should be determined as from 3;: to 12p in the point of experimental view, that is to say,

When the value of x is in the range mentioned above, the value of y is from 3 to 20, namely, the thickness of synthetic resin is from 3 .t to 20 1..

Roughness measurement was made according to JIS BO60l-l955, namely the distance between the upper limit and lower limit of unevenness at any definite length in a cylinder, wherein rarely occurring, uncommonly high values were excluded.

If the roughness is greater than 12;; it is impossible to obtain the advantages and effects of this invention and, if less than 3 p. the working operation becomes difficult.

As mentioned above, the alloy or wear-resistant metal layer is worked within an easily workable range so that the working cost is low and the cylinder, in accordance with the invention, will function effectively from the beginning of its operation by means of the aforementioned resin coating.

For finishing a surface of an alloy or wear-resistant coating within the range of from 0.4;]. to 3 roughness, a #400 honestone should have been used in prior art so that the work efficiency was low and the cost was high.

On the contrary, as the working operation in accordance with the invention is performed only within easily workable limits, the cost is very low. A surface of a cylinder which has been rough finished to avoid high cost has the fault that the running-in-property of the surface against the mating member (piston ring) is low and the wear of the member is great. According to the invention, the surface of the cylinder is worked within an easily workable range and a synthetic resin layer having a good running-in-property is applied on the surface so that the wear of mating member is lowered. Furthermore, the running-in condition will shift smoothly to the normal condition and stable operation will be exhibited during the normal condition period.

The cylinder in accordance with the invention is the same as a conventional cylinder which is worked to the range of from 0.4a to 3p. by mechanical work only. in the points of the function of engine, blow-by, and consumption of lubricant. As mentioned above, the cost of production in accordance with this invention is low and the desired functions of the cylinder are fully exhibited.

EXAMPLE 1 FIG. 2 shows an embodiment of the cylinder liner according to this invention. Numeral 1 is a wear resistant cast iron liner, numeral 2. is a finished surface, and the numeral 3 is a polytetrafluoroethylene layer. In this case, the sliding surface 2 of the cylinder liner 1 is worked to the degree of about 6,.

roughness by means of #150 honestone, and coated with a synthetic resin layer having a thickness of 8 Similar to the conventional process, the process for producing the polytetrafluoroethylene coating is as follows:

Process for Producing Polytetrafiuoroethylene Coating 1. Removal Of Fat Removing by solvent, such as,

trichloroethylene. Rinsing. 2. Liquid Honing.

Rinsing. 3. Drying By air.

gun having 1 mm./d diameter means.

5. Drying Was carried out at room temperature.

6. Baking Introduce the cylinder into a furnace smoothly, and bake under the conditions of 360 C., for about ten minutes. The baking period will be changed according to the dimensions of the goods.

7. Rapid Cooling"--- Strengthen the coating by rapid cooling.

EXAMPLEZ FIG. 3 shows another embodiment of the cylinder liner according to this invention. Numeral l is the cylinder liner made of Al-alloy, numeral 2 is a finished surface, numeral 3 is a polytetrafluoroethylene layer and numeral 4 is hard chromium plating. The cylinder liner is so constructed that the hard chromium plating layer is coated on the inner surface of the cylinder liner, the surface of chromium layer is worked to the degree of about 6;; roughness by means of honestone and then the chromium layer is provided with a polytetrafluoroethylene coating of about 8,u. thickness. The process for producing the polytetrafluoroethylcne coating is the same as that of Example 1.

I claim:

1. A method for finishing a surface of a cylinder liner comprising, working said surface formed ofa wear resistant metal so that it has a roughness within the range of from about By. to about 12 .t. and depositing a polytetrafluoroethylene resin layer on said surface, said layer having a thickness shown by the expression,

et/2 5x +1,

wherein is the roughness of the metal surface and y is the coating thickness, to thereby compensate for the lack of running-in-properties due to the lack of smoothness due to working.

2. A cylinder comprising an inner surface of wear resistant metal worked to a roughness, within the range of from about 1 3 to about 12 and a polytetrafluoroethylene resin layer deposited on said surface. said resin layer having a thickness shown by the expression 

